1. Technical Field
This invention relates to bonding equipment and methods and is particularly concerned with an apparatus and method for bonding together matching sheets of a multi-panel device.
2. Discussion
A multi-panel device serves many functions and is used, for example, as a door or lift gate in vehicles. Such a device is fabricated by securing an inner panel to an outer panel through the use of a bond between adjacent surfaces of the panels brought in contact with each other. The inner and outer panels may be constructed of such materials as steel or plastic. Methods for securing these steel or plastic panels together often used in industry today utilize several liquid adhesive bonding techniques.
Presently, one of the bonding techniques employed by those skilled in the art uses robotic devices to apply an adhesive substance to the contact surface of one of the panels. A second panel is then positioned on the first panel in contact with the surface to which the adhesive was applied. The adhesive material is then cured by applying heat or RF energy to permanently bond the two panels together.
Shortcomings associated with these techniques include difficulties in achieving the desired location, bead size and quantity of adhesive. To address these difficulties, time or labor intensive procedures are typically required to ensure that the adhesive bead is applied to the proper surface location and is of sufficient size to effect a secure bonding of the panels, while preventing the use of excess quantities which may create beads of wasted adhesive around the edges of the bonded panels, collect within non-contacting channels of the panels or escape from the panels to adjacent surfaces. For adhesives which cure at ambient temperatures, the open time (the time available to position the second panel on the first panel before the adhesive cures) places time limitations on bonding techniques that can be successfully used. For example, a power failure on the assembly line after adhesive beads have been applied to several of the panels would result in adhesive curing before the placement of the other panel or panels onto the adhesive-laden panels. Thus, the defect rate when applying an adhesive bead with a robot may be high as a result of these and other manufacturing problems. Because robotic devices are frequently used in these procedures, manufacturing the device becomes more costly.
Expensive sophisticated equipment capable of the detail required for the adhesive application procedure is usually utilized to ensure that the proper amount of adhesive is dispensed and that no excess adhesive is squeezed onto exterior visible surfaces of the panels. Because excess adhesive on these exterior surfaces could cause mechanical malfunctions and aesthetic defects, the robotic device generally leaves skips and voids in its application of the adhesive to avoid adhesive squeeze-out. Robots occasionally encounter problems going around corners of the panels when applying adhesive beads in this manner, however, and the additional programming required to achieve desirable results creates further expenses, both in labor and in time.
The need therefore exists for a new method and apparatus for bonding multi-panel devices which is capable of easily and inexpensively applying the proper amount of an adhesive, without the need for time and labor intensive procedures.